This application claims priority to German Patent Application No. DE 102 07 019.9, filed Feb. 20, 2002, which is incorporated herein by reference in its entirety.
The invention relates to a device and a method for securing filament tufts.
Many clamping methods and devices are known.
For example, U.S. Pat. No. 4,979,782 describes a method and a device for producing bristle products from plastic. In that case, the bristle products include a bristle carrier and bristles. Each bristle is secured at one end to the bristle side surface of the bristle carrier. At their other ends (the xe2x80x9coperating endsxe2x80x9d), the bristles are uniformly rounded. During production of such bristle products, the bristles are clamped in a clamping device while the operating ends are in a flat plane. Thereafter, the bristles"" operating ends are uniformly rounded while they are clamped in the flat plane. The clamp restraining the bristles is then loosened and the operating ends of the bristles are axially displaced relative to one another. In this way, the desired outer bristle contour is achieved.
German Patent No. DE 40 06 325 A1 describes a method for finishing the bristles of a brush. The bristles are clamped at a distance from their operating ends and are cut to the desired length. Then, the bristles are finished using a flat abrasive surface arranged perpendicularly to the alignment of the bristles. The bristles are moved along the abrasive surface""s circular tracks, all of which have the same diameter. To adjust contact pressure, the abrasive surface is moved towards the bristles. To influence the results of finishing, the bristles are restrained laterally by the abrasive surface at a distance between their clamped ends and their operating ends. This distance is adjustable, but is always the same for all bristles.
European Patent No. EP 0 567 672 B1 describes a method for producing toothbrushes with specially profiled bristle tufts inserted in their brush heads. In this method, the final finishing step of cutting and rounding the bristle tufts"" operating ends may be omitted if the filaments to be used are already rounded. The tufts are inserted into through-holes in a clamping device before being affixed to the bristle carrier. The clamping device""s through-holes form a pattern matching that formed by the bristle carrier""s holes. Each through-hole in the clamping device is connected to a clamping member. The bristles"" ends protrude from both sides of the clamping device. While the clamp elements of the clamping device are in the loosened state, a pressure element with a shaped side is moved forward to engage the protruding ends of the bristles. The pressure element presses the bristles axially into the through-holes. In this way, both ends of the bristles are aligned in parallel surfaces, the configuration of which matches shaped sides. Then the clamp elements are used to restrain the bristles in the clamping frame while the ends are aligned. The base ends of the bristles are then inserted into the holes in the bristle carrier.
Finally, WO 01/91607 A2 describes a clamping device for restraining filament tufts of varying sizes in which a movable clamp element is moved between two fixed clamp elements. The filament tufts then pass through apertures in the clamp elements. In the unloaded state, the apertures are aligned.
One problem with known transportation methods in xe2x80x9cspool feeding installationsxe2x80x9d (i.e., brush manufacturing machines in which the bristle material is provided on rolls) arises from the nature of the tufts. Considerable variations in the circumference and diameter of the tufts are unavoidable, since the tufts are produced from individual filaments. In known clamping techniques, the largest tuft determines the highest possible clamping force. Compressing the tufts further causes damage to the filaments. As a consequence, smaller tufts may not be securely clamped and thus may slip out of the clamping apparatus. This problem is exacerbated by the fact that compressibility also varies with the size of the tufts.
In one aspect, the invention features a clamping device including a first clamp element and a second clamp element. The clamp elements comprise clamping plates, and the clamp elements are movable with respect to each other. The clamping plates define an array of apertures, such that the clamping plates can clamp one portion of one filament tuft, while not clamping another portion of the same tuft or another different filament tuft. The clamping device can accommodate tufts of different sizes. As a result, the clamping pressure exerted on each of the various bristle tufts may be optimized for the individual bristle cluster segments formed by the tufts. One advantage to such an arrangement is that it prevents the dislodging of tufts that are too small to be restrained effectively. Another advantage is the avoidance of clamping larger tufts too tightly. Thus, the likelihood of inflicting damage upon larger tufts"" filaments, or of accidentally cutting them, decreases. In a brush manufacturing machine, multiple clamping devices may be deployed one behind the other or side-by-side. Such a clamping device is particularly advantageous for brush manufacturing machines in which the bristle material is provided on rolls, also known as xe2x80x9cspool feeding installationsxe2x80x9d.
In some embodiments, the clamping plates of a clamp element may be arranged in multiple planes, one behind the other, in the direction of the filament tuft. In some embodiments, the clamping plates of a clamp element may include narrow apertures. In some such embodiments, only the narrow apertures exert a clamping force on the filament tufts being passed therethrough, while the filament tufts that are fed through the wide apertures are not clamped. Consequently, each clamping plate clamps only a portion, that is to say only a specific segment, of the complete bristle cluster. All portions taken together then form the complete bristle cluster.
In some embodiments, the clamping plates of a clamp element may be arranged in one plane and parallel to one another in the longitudinal direction of the filament. For example, the clamping plates may move toward, and slide over, one another. Each clamping plate clamps only a portion of the complete bristle cluster. All portions taken together then form the complete bristle cluster. In some such embodiments, only filament tufts that are actually being restrained by a clamping plate also pass through the respective clamping plate.
Some embodiments include multiple clamping plates. By dividing the clamping force among a plurality of clamping plates, it is possible to precisely synchronize the clamping forces acting on the filament tufts. In addition, complicated bristle clusters with the most disparate tuft sizes may be clamped with consistently high-quality results.
In some embodiments, the clamping device includes at least one contact pressure plate for exerting a force on the clamping plates of a clamp element. In some such embodiments, it is possible to apply a load to a specific point of the clamping device (for example, with pneumatic pressure). Alternatively, pressure may be applied by electromagnetic or hydraulic means, though the latter is not so suitable due to the risk of oil leaks and the lower operating speed. In some embodiments, multiple contact pressure plates may be provided, one for each clamping plate of a clamp element. Each clamping plate of a clamp element may then be regulated individually and separately from the others.
In some embodiments, the clamping plates of a clamp element may be subjected to pressure via dampers. For example, metal or plastic compression springs or components made from elastomeric plastic may be used as dampers. This enables apportioned, damped transmission of the centrally generated compressive force to the respective clamping plates. Moreover, the dampers assist in returning the contact pressure plate as soon as the applied compressive force is dissipated.
In another aspect, the invention features a method for restraining filament tufts using a clamping device with fixed and movable clamping plates. The clamping device has at least two movable clamping plates. Filament tufts having varying tuft sizes are fed from a spool feeding installation into the clamping device. The supplied material may, for example, be unwound from one or more spools. The filament tufts are clamped using the necessary clamping force for each tuft size by moving the clamping plates of a clamp element relative to the clamping plates of another clamp element. At least two segments are created in the bristle cluster formed by the filament tufts. In this way, the clamping force is defined both by the tuft size and the maximum permissible clamping force to avoid damaging the filament tufts. An optional finishing step may be performed, and then the filament tufts are transferred, and the clamping plates are released.
In some embodiments, the bristle tufts may already be arranged in a desired bristle cluster form, for example on the brush head of a toothbrush. All process steps are fully automatic and are executed at high speed. By dividing the filament tuft that is grasped by the clamping device into two or more segments, a reliable process is enabled that assures consistently high product quality. It is also advantageous that the clamping device include as many segments as possible for accommodating complicated bristle clusters.
In some embodiments, the method includes an additional step of adapting the compressive force via the dampers to match the respective tuft size in the individual segments. The dampers may be compression springs, for example, and may be made from metal, plastic, or elastic components made from rubber. In addition to the adjustment of the compressive force on the contact pressure plate, a further adjustment capability is the selection of the desired elastic resiliency.
In some embodiments, the method includes rounding and/or cutting the filament tufts to size as a finishing step. Other finishing steps, multiple finishing steps or even no finishing steps are possible.
Implementations of the invention may have one or more of the following advantages. The incidence of filament tufts slipping out of the filament feed device because of inadequate clamping force due to varying tuft sizes may be eliminated. The range of variation in the individual filament tuft diameters may be reduced. Damage to filaments as a result of excessive clamping force may be effectively eradicated.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.